1. Field of the Invention
This invention relates to a fuel supply system employing an ultrasonic vibratory member of a hollow cylindrically shaped body. 2. Description of the Prior Art
An ultrasonic vibratory member of a hollow cylindrically shaped body affords the advantage of providing an extremely increased amount of atomized fuel, because of an extremely wide atomizing surface, as compared with an atomizing means using the end of an ultrasonic wave horn as an atomizing surface, and another type atomizing means in which a disc member is secured to the tip of the ultrasonic wave horn of the type described, so that fuel may be atomized on a circular surface of the disc member.
Hitherto, however, it has been a general practice for supplying fuel to a vibratory member of a hollow cylindrically shaped body to supply fuel to one spot on each of the inner and outer peripheral surfaces of the ultrasonic vibratory member, or to two or more positions corresponding to nodes of vibrations on the inner and outer peripheral surfaces of the vibratory member at the time of ultrasonic vibrations. Therefore, the prior art fuel supply systems provide a danger that in case an excessive amount of fuel is supplied instantaneously, part of the fuel fails to be atomized, but is repelled back from the surface of the vibratory member. In addition, in case an extremely small amount of fuel is supplied, the fuel tends to be supplied in the form of large drops, thus failing to reach an atomizing surface of the vibratory member, resulting in incomplete atomization of fuel. In addition, fuel is supplied to a specific spot or spots, resulting in corrosion and short service life.
Meanwhile, major items of requirements for an automotive internal combustion engine are (1) improvement in fuel consumption, (2) emission control of exhaust gases, and (3) improvement in drivability. To meet these requirements, various attempts have been proposed for modification of engines. The most important factor affecting the aforenoted requirements is a method for supplying fuel to an engine. What is of the supreme importance to this end is to provide fuel in the form of droplets as fine as possible, thereby achieving thorough mixing of air with atomized fuel. This may minimize the amount of fuel required for combustion chambers, without clinging of fuel to the inner surfaces of an intake manifold and the like, thereby improving fuel consumption. In addition, the condition of combustion may be improved to a degree to enable complete combustion, thereby minimizing the amounts of carbon monoxide and unburned hydrocarbons, i.e., harmful constituents of exhaust gases, which are produced due to incomplete combustion. Still furthermore, the flow speeds of fuel and air become almost constant, so the engine response may be improved, with an accompanying improvement in drivability.
Furthermore, upon cold starting, an automotive gasoline engine, as the Otto engine, remains as a whole at a low temperature with the result of a poor vaporization of the fuel. For example, in some cases, the air-fuel ratio admitted into the cylinder (combustion chamber) becomes 20, even in the case where the fuel has been supplied through a carburetor or a fuel injector at an air-fuel ratio of about 13. In such cases, a liquid of excessive fuel flows along the inner wall surfaces of the intake pipe and reaches the cylinder with a certain time delay. Therefore, it has been necessary either to provide a choke and idle fuel supply system for a carburetor or to add a cold start injector in the case of a fuel injection system, to thereby supply a mixture of an air-fuel ratio of 8 to enable supply of a mixture of air-fuel ratio of about 13 to the cylinder during a cold start.
In the operating range of the engine from warming up to low r.p.m. and low load, it is difficult to maintain an intended air-fuel ratio since the total flow rate of fuel is too small to enable its precise measurement. In addition, the flow rate of air is insufficient to atomize the fuel into fine droplets of suitable sizes.
These factors necessarily lead directly to increased fuel consumption, uneven air-fuel ratio distribution among respective cylinders, wide variations in air-fuel ratio in terms of time, impaired combustion, poor drivability and emission of harmful gases.
During engine operations under conditions other than the above-mentioned conditions, the control of the fuel flow is easier, as the amount of the intake air and the flow rate of the fuel are increased with an increase in load. However, it is still desired to preclude the flow of fuel in the form of liquid from the viewpoints of the engine response and the inter-cylinder air-fuel ratio distribution which exerts a great influence on emission of harmful gases.
Throughout all operating conditions of an Otto cycle engine, it is a pressing need to remove the liquid flows of the fuel along the inner surfaces of the intake pipe between the fuel supply system and an intake valve by atomizing such fuel into droplets of suitable sizes, and this invention contemplates to provide a solution to this problem.